Printer-Friendly Version

If you have applied the macOS Catalina or Big Sur upgrade, you may have noticed a new volume on your Mac, "Macintosh HD - Data". This new volume is part of a volume group, which is a new concept that Apple introduced in macOS Catalina. We discuss volume groups in detail here, but the remainder of this article aims to answer your questions about how CCC handles this new volume structure and what you have to do, if anything, to adjust your backups for Apple's latest OSes.

Maybe. If you are making a simple backup of your startup disk to a dedicated backup disk, then no, you do not have to make any changes to the destination unless CCC specifically recommends it. CCC will automatically make the changes required for your destination to be a bootable backup of your startup disk. If your destination volume is encrypted, however, see the question later in this document for information specific to encrypted destinations.

If you have multiple tasks that back up to the same destination, however, then now is a good time to revisit your backup "hygiene". Ideally, each source that you back up will have a dedicated volume on the destination. This is particularly important when one of the sources is a Catalina or Big Sur startup disk. See this section of CCC's documentation for guidance on how to configure your destination device to accommodate backups of multiple source volumes:

I want to back up multiple Macs or source volumes to the same hard drive
Video: Preparing your backup disk on macOS Catalina (and later)

No. When you select your startup disk (e.g. Macintosh HD) as the source for your backup task, CCC will automatically back up both volumes in that volume group.

Many external hard drives are shipped with a Windows-centric format and partitioning scheme. That partitioning scheme can't accommodate Apple's APFS filesystem, so before you can use your backup disk for making a bootable backup of your startup disk, you must make sure that it is partitioned with the correct partitioning scheme. This section of CCC's documentation walks you through the steps for configuring your backup disk:

Preparing a hard drive for use with Carbon Copy Cloner

Disk Utility's interface for performing this simple task is surprisingly unintuitive, so here is a summary of the process with some emphasis on the steps where people often go awry:

  1. Open Disk Utility
  2. Choose Show all devices from Disk Utility's View menu. This is a very important step!
  3. Choose the parent device of your destination volume in the sidebar – don't click on the backup volume itself, click on its parent device. If you don't click on the parent device, you won't be able to change the partition scheme.
  4. Click on the Erase button in the toolbar. Don't click on the Partition button! That would seem like the obvious choice, but you cannot actually change the partitioning scheme in the Partition interface.
  5. Set the Scheme to GUID Partition Map and the Format to APFS, then click the Erase button.

If you're still having trouble correcting the partition scheme, you may find this video demonstration helpful.

Because macOS leverages volume groups for the startup volume, creating a bootable backup requires an APFS formatted destination volume. HFS+ is no longer an option for booting macOS starting with macOS Catalina. For your convenience, CCC will automatically convert your HFS+ formatted backup volume to APFS as necessary and create a volume group on the destination. This conversion is the same conversion that took place on your startup disk when you upgraded to High Sierra or Mojave, with one notable exception: CCC tells you that it's going to convert the destination, and gives you the opportunity to decline the conversion. The conversion is non-destructive — any data that you have on the destination volume will remain in place, the only thing that changes is the format of the volume.

Typically there is no reason to decline the conversion. The conversion is non-destructive, and it's required for making a backup of the system. If your backup volume is dedicated to your CCC backup task, then converting the destination to APFS is the right choice.

However, if your destination volume is not dedicated to your CCC backup task or if you're not intending to back up the macOS System files, you should consider how the other uses of your destination might be affected by the conversion. For example, Time Machine is not currently compatible with APFS as a destination, so converting a destination volume that contains a Time Machine backup would break the Time Machine backup. CCC specifically avoids converting Time Machine backup volumes. Another example – if you're only backing up a single folder or handful of folders from your startup disk, you should configure a folder-to-folder backup instead, which won't require any conversion of the destination.

You should also avoid the conversion if your destination device is a slower 2.5" rotational HDD, i.e. with a rotational speed of 5400RPM (or slower!). APFS does not perform well on HDD devices, and that performance is unacceptable on these slowest HDD devices due to their much slower seek performance. Keep these slower disks formatted as Mac OS Extended, Journaled. These devices are suitable for Data-only backups, but you should acquire an SSD for making bootable backups.

No. In particular, you should not use the Finder to copy items to the root level of your bootable backup disk. Finder will copy that data to System volume within the group, and when the System volume is subsequently updated, any non-system files could be permanently deleted from that System volume. If you want to store other items on your backup disk that are unrelated to the backup of the system, create a separate volume on that disk for that purpose (see the following question for instructions).

Video: Backing up multiple sources to a single APFS-formatted device

If your destination volume is already APFS formatted, but you do not want to make your bootable backup in that volume, you can simply add a new volume to the existing APFS container:

  1. Open Disk Utility
  2. Select your destination disk in Disk Utility's sidebar
  3. Click the "+" button in the toolbar

If your destination volume is not APFS formatted, and you cannot or prefer to not convert the volume to APFS, you can create a dedicated partition on your destination disk for CCC to use. To create the partition:

  1. Open Disk Utility
  2. Select your destination disk in Disk Utility's sidebar
  3. Click the Partition button in the toolbar
  4. Click the "+" button to add a partition to the disk
  5. Set the name and size of the partition to your preference
  6. Choose APFS as the format
  7. Click the Apply button

If you were keeping other data at the root level of your backup disk that isn't on your startup disk, then that data is still on your backup disk, but it will be harder to find in the Finder due to the volume group changes that are applied for a backup of the startup disk. If your backup disk is named "CCC Backup", right-click on the "CCC Backup - Data" volume in CCC's sidebar and select Reveal in Finder to reveal that content.

Video: Backing up multiple sources to a single APFS-formatted device

It depends on how much data you have on your destination volume, the performance of the destination device, and the degree to which the destination volume is fragmented. It can take a while, but CCC won't wait for more than two hours for the conversion to complete. If it's taking longer than two hours, then CCC will recommend that you erase the destination volume instead, which will resolve any performance issues that are directly caused by filesystem fragmentation. If CCC issues this recommendation and you prefer to wait out the conversion rather than erase the volume, you're welcome to convert the volume in Disk Utility instead (the option is in the Edit Menu).

Unfortunately that is not possible due to a macOS limitation, Disk Utility cannot add an encrypted volume to an APFS volume group. When you select a Catalina+ startup disk as a source and an encrypted volume as a destination, CCC will disallow the selection and suggest that you erase or decrypt the destination volume.

Fastest and easiest solution: Erase the destination as APFS (not encrypted)

Erasing the destination volume is the simplest and fastest way to resume your bootable backups, and you can find detailed instructions for doing that here: Preparing a hard drive for use with Carbon Copy Cloner.

After you have run your backup task to a non-encrypted volume, you can then boot from the backup and re-enable FileVault in the Security & Privacy Preference Pane.

Related Documentation

Decrypting the destination volume will take considerably more time (possibly days) and effort, but you can decrypt the destination volume with one of the following methods:

A: Boot from the backup volume, open the Security Preference Pane, disable FileVault

B: Decrypt the volume in the Terminal application. E.g. for an HFS+ formatted destination:
diskutil cs decryptVolume "/Volumes/CCC Backup"

Or for an APFS-formatted destination, get a list of user IDs associated with the encrypted volume, then use one of the "Local Open Directory User" UUIDs from the output of the first command with the second command:
diskutil ap listUsers "/Volumes/CCC Backup"
diskutil ap decryptVolume "/Volumes/CCC Backup" -user B44348A3-68DF-4B7B-800D-47FE38711178

Replace "B44348A3-68DF-4B7B-800D-47FE38711178" with a UUID produced by the first command.

Wait for decryption to complete

You'll have to wait for the decryption process to complete before you proceed with your backup task. Decryption will continue in the background while you're booted from your production startup disk. macOS doesn't offer a convenient method to see conversion progress, but you can type diskutil apfs list (or diskutil cs list if the applicable volume is HFS+ formatted) in the Terminal application to see conversion progress.

Re-enabling FileVault on your bootable backup volume

After you have run your backup task to a non-encrypted volume, you can then boot from the backup and re-enable FileVault in the Security & Privacy Preference Pane.

Related Documentation

No, this is a one-time task that is required for CCC to be able to make adjustments to the destination volume that are required for APFS volume groups. Once you have established a bootable backup, you can reenable FileVault and your future backups will work without any additional intervention.

If you are willing to forgo the creation of a bootable backup of your startup disk, you can configure your backup task to back up only the Data volume of your startup disk:

  1. Open CCC and click the Show Sidebar button in CCC's toolbar if it is not already visible
  2. Select your backup task in the sidebar
  3. Drag the Macintosh HD - Data volume from CCC's sidebar into the Source selector
  4. Save the task

With this configuration, CCC will not impose any requirements on the format or encrypted nature of the destination volume. Because this destination will not be bootable, we recommend that you remove any existing System folders from the destination volume to avoid any ambiguity about the functionality that this volume provides.

If your backup disk is a "mobile" 2.5" rotational disk (i.e. that spins at 5400RPM or less), we recommend that you format that device as "Mac OS Extended, Journaled" (aka HFS+) and use it for data-only backups. APFS offers unacceptable performance on these devices, we simply can't recommend nor support the use of these devices for bootable backups.

Yes. Your startup disk has two separate volumes, a read-only System volume, and a writable Data volume where all of your data is kept. The System volume has about 10GB of content, and CCC will back that up first. When CCC has finished copying the System volume, CCC will then proceed to back up the contents of your Data volume. The System volume will only get modified when you apply macOS updates, though, so you won't see this volume getting copied frequently — CCC will only update the System volume on the destination when the System volume on the source has been modified.

Watch a video of this tutorial on YouTube

Yes, you can dismantle a volume group in Disk Utility. You may want to do this if, for example, you cloned your startup disk to a volume that was not intended to be dedicated to your backup task. The procedure is relatively simple — you simply delete the System volume, then rename the Data volume, then remount the volume. If your backup disk was named "CCC Backup", for example, you would do the following:

  1. Open Disk Utility
  2. Choose Show all devices from the View menu
  3. Select the CCC Backup volume in the sidebar — this is the System volume in the group.
  4. Click the button in the toolbar to delete that volume
  5. Select the CCC Backup - Data volume
  6. Click the Unmount button in the toolbar
  7. Click the Mount button in the toolbar to remount that volume
  8. Change the name of the volume back to CCC Backup

You won't find a legacy _CCC SafetyNet folder on the destination if snapshot support is enabled on that volume. Instead, select the destination Data volume in CCC's sidebar to see a list of SafetyNet snapshots.

If snapshot support is not enabled on your destination volume, then the SafetyNet folder can be difficult to navigate to in the Finder. It's still located at the root level of your destination's Data volume, but the Data volume is hidden by default in the Finder. To reveal it in the Finder, click on CCC's Destination selector and choose the Reveal Data Volume option.

If you have ever restored content back to your production startup disk while booted from a CCC backup, then there may have been a _CCC SafetyNet folder placed at the root of that volume. When you upgrade to Catalina or Big Sur, the macOS installer will relocate any content that is at the root of the startup disk to Users > Shared > Relocated Items > Security. You will also find a PDF in that folder explaining why the content was moved there. In short, the content was moved there because it is very difficult to find content at the root level of the Data volume of your startup disk.

If you attempt to delete that SafetyNet folder (and you certainly may delete that folder), the Finder may claim — falsely — that the folder cannot be deleted because some items are in use. In fact, nothing in that folder is in use, but some of the older system items may be protected by System Integrity Protection. You can learn how to dispose of this content in this section of CCC's documentation:

Why can't I delete some items from the SafetyNet folder? The Finder says that some items are in use.